In which scenario would a gas behave least ideally?

A gas behaves least ideally under conditions of high pressure and low temperature. At high pressures, the gas molecules are forced closer together, which increases the effects of intermolecular forces that are typically minimized in ideal gas behavior. As the distance between particles decreases, these attractions and repulsions become significant, causing deviations from the ideal gas law, which assumes no intermolecular forces are present.

In addition, at low temperatures, gas molecules have lower kinetic energy, leading to slower motion. This again increases the potential impact of intermolecular attractions, as the molecules do not have enough energy to overcome these forces effectively. Therefore, under high pressure and low temperature, gases exhibit characteristics that differ from ideal gas predictions due to these intermolecular interactions and reduced kinetic activity.

In contrast, under high temperature and low pressure conditions, gas molecules are far apart and moving rapidly, which allows them to behave more ideally as the effect of intermolecular forces is minimized. Moderate pressure and temperature typically present conditions that closely approximate ideal behavior as well. Low volume and low pressure also lean towards ideal gas behavior, as the conditions help maintain minimal interactions between particles.